Contact for rheostats and method for affixing the same



AME

'Feb. 27, 1934. D. T. SIEGEL CONTACT FOR RHEOSTATS AND METHOD FORAFFIXING THE S Filed Jan. 28, 1931 lmlll'lnllbll lh llllmw Patented Feb.27, 1-934 CONTACTFOR RHEOSTATS AND METHOD FOR AFFIXING THE SAME Davidsiege, Chicago, n1.

Application January 28, 1931. .Serial No. 511,766

I ClaimsL (Cl. 201-55) This invention relates to rheostatsand is moreparticularly directed to improvements in contact points on theresistance element thereof.

One object of my invention is to insure better I I contact between theresistance wires and the contact arm-wiper.

Another object of the invention is to over-' come the undesirableeffects of the oxidation of resistance elements of rheostats.

A further object is to provide a smooth contact surface caused by theinevitable constant rubbing thereof by the arm-wiper.

A further object is to increase the surface of the contact unit and thusto spread and diminish l5 theheatproduced.

A further object of the invention is to provide an economical method ofeffecting 'the'above and other objects.

In the drawing:

Fig. l is a plan view of a rheostat with the cover in place. I

Fig. 2 is a plan view of a rheostat with the cover removed showing theresistance wires and the contact arm-wiper.

Fig. 3 is an enlarged view similar to Fig. 2 with metal contact pointsaffixed to the resistance wires.

Fig. 4 is a plan view of the disc used for affixing the metal. contactpoints.

Fig. 5 is a perspective view showing the metallic contact points beingsprayed with the disc (Fig. 4) in position on the resistance wire of therheostat (the contact arm-wiper in this view being removed.)

The same numbers are given to like parts in the various/figures of thedrawing.

In the drawing 1 is the case of a rheostat and I -2 is the knob of thecontact arm-wiper journalled on the pin 3. 4 is the contact arm-wiper 4and that part thereof contacting with the resistance wire 6. 7 are themetallic contacts affixed to the resistance wire 6. 8 are theperforations in the circular disc for forming the metallic contacts '7.9 is one form of jet or a 5 mechanism for spraying the metallic contactpoints 7 through the perforations 8 of the circular disc.

In the smaller rheostats heretofore used, the contact arm-wipercontacted directly with the 5 resistance wires, and in the largerheostat in which brass contact points were used, the same were aflixedby means of being embedded in the witreous enamel or by means entirelydifferent from the inexpensive means set forth herein.

Due partly to the comparative thinness oLthe resistance wires but mainlydue to oxidation, the contact between the arm andv the wires hasfrequently been very poor, resulting in materially reduced efficiency ofthe resistance unit. By I means of metallic contact points such as brass00 and the like which are comparatively free from oxidation, thementioned defect heretofore existing is overcome and the efliciency oftherheostat is materially increased, resulting in smoother and moreefficient operation. 4

The metallic contact points may be applied substantially in thefollowing manner: v A disc of metal or card-board or other suitablematerial, preferably of substantially the same, orlarger, diameter asthe rheostat to be effected, 10 having perforations equivalent to thedesired number and size of the metal contacts. to be formed, is placedupon the resistance wires of the rheostat with the contact arm-wiperremoved.

By means of the greater radiatingsurface of 5 the brass contactpoints,-the heat will be spread, and will be more readily dissipatedespecially since brass has a high degree of heat' conductivity.

I prefer to use brass rather than other metals on because of its economyand utility,- because aluminum wears off. to quickly, copper is subjectto a far greater degree of oxidation and platinum and tungsten are farmore expensive. It will be understood, however, that while I use brassas '95 the preferred form, I do not conflnemyself to any particularmetaL- The jet shown in the drawing is one large enough to cover theentire disc although it will be obvious that a smaller jet or mechanismmay be 1 used and each contact point may be sprayed separately or ingroups.

It is obvious, as I have found by actual experiments and tests, thatwhen contact is made 7 by means of the arm-wiper and the metallic con- 15 tact points that far greater e'fliciency results than has heretoforebeen obtainable.

Although I have shown the preferred form of my invention yet it will beunderstood that I do not limit myself to the drawing shown or the 1specifications recited but include all forms and variations of thedevice and method which do not depart from the spirit and scope of myinvention.

Having described my invention and explained the manner of its use, whatI claim and desire to secure by Letters Patent is:

1. A rheostat of the type described comprising a core member, aresistance wire wound thereon, a contact element in adherent union withand at a plurality of spaced points on said wire, said contact elementadapted to be adhered between parallel lengths of wire and also upon thesurface of said core, and an arm adapted to coact with said contactelement.

2. An article of the class described comprising a core member having acircular central open- ,ing therethrough, a winding thereon arranged ina'series of loops encircling saidcore member, a plurality of regularlyspaced contact members connected to groups ofloops of said windings,said contact members comprising an adherent metal secured to said wiresand to the surface of said core member.

3. An article of the class described comprising a core member having acircular central opening therethrough, a winding thereon arranged in aseries of loops encircling said core member, a plurality of regularlyspaced contact members con- 4. A rheostat having a solid core in theform of a flat disk and having a medial opening therethrough, aresistance wire wound upon said core and bearing against the surfacethereof, and a plurality of contact portions of adherent materialsecured to the turns of the wire and to the surface of the core member.

5. A rheostat having a solid core in the form of a flat disk and havinga medial opening therethrough, a resistance wire wound upon said coreand bearing against the surface thereof, and a plurality of similarlyshaped contact portions of adherent material secured not only to theturns of the wire but also to the surface of the core member.

6.- The method of manufacturing rheostats which consists in the steps ofwinding a resistance wire upon a core member, depositing a molten metalat spaced intervals around the periphery of said core member andallowing the same to' cool in this position whereby the same adheresboth to the wire and to the surface of said core member. v

7. The method of manufacturing rheostats which consists in the steps ofwinding a resistance wire around a core member and then depositingrectangularly shaped spots of molten metal upon a surface of said coremember at spaced intervals around the periphery thereof, said moltenmetal being capable of adhering upon cooling both to the wire and to thesurface of said core member.

Dav n 'r. 'SIEGEL.

